Communication is one of the fundamental components of human and non-human animal behavior. The lateral belt of the auditory cortex (LB) in rhesus monkeys has recently been identified as a cortical area that plays an important role in vocalization processing. This grant application, which uses auditory-object analysis as a theoretical framework, tests the role of LB neurons in processing communication signals, both species-specific vocalizations and human spoken words. In Aim 1, we test the capacity of neural activity in the lateral belt (LB) to differentiate between different vocalizations (auditory objects). We hypothesize that (1) LB neurons preferentially code different vocalizations as opposed to their spectrotemporal acoustic features and that (2) the capacity of LB neurons to code different vocalizations increases as the number of simultaneously tested neurons increases. In Aim 2, we test the hypothesis that LB neurons respond in a categorical manner. Moreover, we hypothesize that the neural sensitivity of individual LB neurons mirrors the monkeys'perceptual sensitivity. This Aim is accomplished by obtained extracellular recordings of LB neurons while monkeys participate in a delayed category-to-match task. During this task, the monkeys categorize two human phonemes and morphed versions of these phonemes. In Aim 3, we test the hypothesis that LB activity is less sensitive to the variance that occurs naturally in vocalizations than to types of variance that are not found naturally. We also hypothesize that this sensitivity mirrors the monkeys'behavioral sensitivity. This aim is accomplished by correlating recordings of LB neurons with the monkeys'performance on a delayed category-to-match task. During this task, the monkeys categorize vocalizations and these sets of artificial stimuli.